Note: Descriptions are shown in the official language in which they were submitted.
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EXPANDABLE MODULAR SWITCHING UNIT
This invention relates to a cabinet or housing which holds
a number of modules or printed circuit boards in a manner that
permits easy insertion and removal of the modules.
With the change of the market from telephone equipment
purchased or rented from a telephone company to telephone
equipment purchased from a manufacturer of telephone equipment
and installed by the customer, there has been an increased demand
for modular expandable equipment and systems. The cabinet and
related equipment of this invention are particularly suited for
such a system because they can provide a small or medium size
switching unit that may be readily expanded or changed. The
equipment of this invention may, of course, be easily adapted for
use in computer systems or in any other system where it is
desirable to expand or change the system to meet new
requirements.
Hereinafter the term modules will be used and it is intended
to include printed circuit boards with components mounted
thereon, and printed circuit boards with components mounted
thereon and sealed in plastic to form a block or mounted in a
casing (with, of course, connecting contacts exposed).
It is known to have a cabinet with contacts on the inner
side of the rear wall for engagement with contact members on any
module. The modules may be disengaged or removed from the
cabinet by gripping finger grips on an outer edge of the module
and pulling outwards. A module is inserted by placing the
contact members on the rear edge against the contacts on the rear
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wall and then pressing the module inwards towards the rear wall.
Guide members or guide walls may be used to ensure the module is
positioned with its contacts against appropriate contact members.
It usually requires two hands to conveniently insert or withdraw
a module, with one hand at the top and one hand at the bottom of
the exposed side of the module.
The contact members or connectors on the module which
engage and grip the contacts in the cabinet normally have a
considerable spring bias to ensure good and reliable contact is
made.
Good contact is, of course, essential. However a large
spring bias frequently makes it difficult to engage manually the
contact members of a module and the corresponding contacts of a
cabinet. A number of means have been devised to provide some
form of force to assist in the insertion and removal of a module.
One such arrangement is described, for example, in Canadian
Patent No. 1,124,346- Jordan, issued May 25, 1982, where a
pivoted lever on a faceplate or cover plate engages a slot in the
cabinet to press the printed circuit board inwardly or outwardly.
This arran~ement adds considerable structure to the cabinet and
board.
Another arrangement is described in United States Patent
No. 4,313,15~ - Chu, issued January 26, 1982. This arrangement
comprises printed circuit boards with a pivoted lever at both the
top and bottom of the exposed ed~e of the board. The structure
may be less complex than that described in the aforementioned
Jordan patent, but insertion and withdrawal requires two hands.
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The cabinet and the modules of this invention use a pivotal
movement for inserting and withdrawing a module. Each module has
at one corner a slot or recessed bearing surface for receiving
a pivot pin or hinge pin. The module is inserted and guided
towards the pin so that the slot moves over the pin. Then the
module is rotated around the pin until contact members at the
rear edge of the module engage contacts within the cabinet. When
the module is rotated about the pin, it acts as a lever. No
complex arrangements are required to press the contacts into the
contact members. The hinge pin locates the module longitudinally
and guide members on the rear cabinet wall locate the module in
a transverse direction to align the contacts with the contact
members. The insertion and withdrawal is essentially a
one-handed operation. The pivot pin locates the module
longitudinally and guide members on the rear cabinet wall locate
the module in a transverse direction to align the contacts with
the contact members. The insertion and withdrawl is essentially
a one-handed operation.
- It is therefore an object of the invention to provide a
module mounting cabinet and modules having in one corner a pivot
pin receiving slot whereby a module may be positioned with the
slot over the pivot pin in the cabinet and the module rotated
about the pivot pin to engage contacts on the module with contact
members in the cabinet.
It is therefore an object of the invention to provide a
module mounting cabinet and modules having in one corner a hinge
pin receiving slot whereby a module may be positioned with the
slot over a hinge pin in the cabinet and the module rotated about
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the hinge pin to engage contacts on the module with contact
members in the cabinet.
It is another object of the invention to provide a
combination of a module and a cabinet where the module is mounted
in the cabinet by positioning the module and rotating it.
Accordingly there is provided a cabinet for an expandable
electronic system for removably mounting modules having circuitry
for connection with the system, comprising a base member in the
cabinet, a transversely extending hinge means mounted to the base
and spaced outwardly therefrom, at least one module having an
inner edge, an outer edge and first and second end edges, the
module having circuitry therein, the module having on the first
end edge adjacent the inner edge a hinge means receiving .~-lot,
and first contact means on the inner edge of the module adJacent
the second end edge connected with the circuitry of the module,
and mating second contact mean~ on the base member for
interconnection with the ~1ectronic system, the module being
adapted to recelve the hinge means in the hinge means receiving
slot and t~ be rotated about the hinge means to engage the first
O contact means with the second contact means.
Embodiments of the invention will be described with
reference to the accompanying drawings, in which:
Figure 1 is a front view of a cabinet according to the
invention;
Figure 2 is a sectional view taken on line 2-2 of Figure 1;
2 ~ ~
Figure 3 is a sectional view taken on line 3-3 of Figure 1
with a top cover shown in section and with a module positioned
for rotation;
Figures 4A and 4B are sectional views of two forms of module
each taken on line 4-4 of Figure 3;
Figure 5 is a partial sectional front view of the lower
portion of a base of a cabinet of another form of the invention;
Figure 6 is a sectional view showing a single pin of a pin
header; and
Figure 7 shows portions of a module mounted in a cabinet and
useful in describing the invention.
Re~erring first to Figures 1 and 2, there is shown a front
view and a sectional side view of a housing or cabinet 10
according to the invention. A rear portion or base 11 may
conveniently be injection molded with spaced guiding ribs 12 and
spaced guiding walls 14. Each guiding rib 12 is located
substantially midway, in a transverse direction, between an
adjacent pair of partitioning or guiding walls 14. Each adjacent
pair of guiding walls 14 is spaced apart by a distance slightly
greater than the width of a module (to be described subsequently)
which mounts between them.
The base 11 has two strengthening regions 15 and 16 which
are transversely extending, generally V-shaped, deformations in
the base 11. The inwardly extending peak of the strengthening
region 15 has a transversely extending supporting bar 17.
Mounted to base 11 on lugs 18 is a distribution printed circuit
board 20. Printed circuit board 20 has circuitry for
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interconnecting the contacts or pins (not shown) in connector pin
header 21 and for making connections to external wiring of an
electronic system (not shown). A hinge pin or pivot pin 22
extends transversely between guiding walls 14. The connector pin
headers 21 are preferably mounted as far from the hinge pin 22
as is conveniently possible as will subsequently be explained.
Referring now to Figure 3, a cross-sectional view of base
11 is shown with a module 23. In Figures 4A and 4B there are
shown cross-sectional views of different forms of module 23. In
Figure 4A module 23 is shown as a printed circuit board 24 on
which various electrical components (not shown) may be mounted,
and a cover board 25 spaced from printed circuit board 24 to
provide space for the components. The printed circuit board 24
and the cover board 25 form a protected circuit pad or sandwich
conveniently filled with a plastic material 27, such as a foamed
plastic material.
A connector receptacle 26 is mounted in the module 23 and
has contact members (not shown) which are connected to the
circuitry of printed circuit board 24. The connector receptacle
26 may, ofcourse, be positioned at any desired place between the
printed circuit board 24 and the cover board 25 so that it will
engage the connector pin header 21. The connector receptacle 26
is at the edge of module 23 with the contact members which it
contains exposed. The module 23 has a curved recess or slot 28
for receiving hinge pin 22, and a recess or indentation 30 which
forms a finger grip. Module 23 also has a supporting slot 31
which is shaped to conform to supporting bar 17.
131~2~6
In Figure 4B, a split casing 29 encloses a printed circuit
board 24A with a connector receptacle 26A mounted therein. The
printed circuit board 24A may be fastened to casing 29 using
screws (not shown) into raised positioning areas 34.
It will be apparent from Figure 3 how the module 23 is
installed. First, the module 23 is positioned with a corner 33
(adjacent slot 28) against the appropriate guiding rib 12 and
between the appropriate pair of partitioning or guiding walls 14.
The module 23 is then moved downwardly along the guiding rib 12
until slot 28 engages hinge pin 22. Then the module 23 is
rotated about hinge pin 22, as indicated by arrow 32, until
connector receptacle 26 mates with connector pin header 21 and
the contact members in connector receptacle 26 engage the
contacts or pins in connector pin header 21. As the contacts and
16 contact members become fully engaged, the supporting bar 17
engages the supporting slot 31 first to provide additional
support and second to provide a stop.
As is indicated in Figure 3, a top cover may be mounted to
base 11 using screws (not shown) through cover mounting studs 36
in base 11 and into screw receiving member 37 in cover 35. Top
cover 35 has a latching hook 38 for each module, arranged to hook
or latch the corner 40 of a respective module 23 to secure it in
its mounted position.
A module 23 may be removed by raising the latching hook 38,
gripping the finger grip 30, rotating the module 23 about hinge
pin 22, and lifting the module 23 off the hinge pin 22. This is
a simple single-handed operation.
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Referring now to Figure 5, there is shown a sectional front
view of a lower part of base 11 with partitioning or guiding
walls 14 and guiding ribs 12. This form of base 11 is open at
the bottom and has parallel air directing members 41 for
directing air flow upwardly past the modules 23 for cooling. The
air directing members 41 in base 11 are useful when a cover is
installed, such as is indicated in Figure 3 by broken lines, as
cover 42.
It was previously indicated that the pin header 21 should
be mounted as far as conveniently possible from hinge pin 22.
There is, in fact, a minimum distance that is acceptable between
hinge pin 22 and the nearest pin in pin header 21, and this
distance depends on the length and permissible amount of bending
or flexing of the pins in pin header 21. By way of example, one
standard in use at pressnt requires a pin length of 0.305 inch
above the header base or printed circuit in which the pin is
mounted. This standard provides that the pin shall be capable
of bending or flexing by plus or minus one degree. This is
approximately equivalent to plus or minus 0.005 inch deflection
at the pin tip. This is illustrated in Figure 6 where a pin 45
is shown mounted in and projecting from a pin header base 46.
This standard, which is used as an example only, will re~uire
certain restrictions in the design. This will become clear with
reference to Figure 7.
Referring to Figure 7, there is shown in abbreviated form,
a distribution printed circuit board 20 in section, with a pin
header 21 having shown two pins 45 and 45A. It will be apparent
that there are normally a greater number of pins in a pin header
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but only two are shown for simplicity. A module 23 is indicated
in partial outline as it would be positioned when inserted or
mounted with hinge pin 22 within slot 28. The connector
receptacle 26 has received the pin header 21 and the pins in pin
header 21 have been gripped or contacted by the contact members
47 (only one pair of contact members 47 are shown for ease of
drawing and this pair are in engagement with pin 45) in connector
receptacle 26.
It will be apparent that the rotation of module 23 about
hinge pin 22 when the module is being inserted or mounted, will
cause a flexing or bending or tilting of each pin in pin header
21. This is because the module 23 and the connector receptacle
26 follow an arc when the module is rotated into engagement. The
pin 45, that is the pin in pin header 21 closest to hinge pin 22,
is the critical pin as it will be tilted or bent by the greatest
amount. The distance M between the center of hinge pin 22 and
pin 45 will determine the amount by which pin 45 will be tilted
or bent. It can be calculated that a distance M of 18 inches
would provide an angle A of one degree, and this would limit the
tilting or bending of pin 45 to one degree. It should be noted
that hinge pin 22 is spaced outwardly from base 11 (Figures 2 and
3) by a distance which will place the hinge pin 22 in a neutral
position, that is, will place hinge pin 22 in a plane defined by
the ends of pins 45 in pin header 21. In the example given
above, this would be of the order of 0.305 inch from the plane
defined by distribution printed circuit board 20. Also, slot 28
in module 23 is located so that it will permit the connector
receptacle 26, and the adjacent module edge, to abut the printed
circuit board 20 with the inner module edge substantially in a
plane defined by the surface of printed circuit board 20.
It will be apparent that other standards for the pins in
pin header 21, which specified shorter pin lengt~s or permitted
greater bending or tilting of the pins, would reduce the distance
M in Figure 7.
It will be seen that the invention providzs for a system
incorporating a cabinet and modules where the modules are readily
added or removed to expand or change the system. The lever
action of the rotating module provides an adequate force to
overcome any resistance caused by spring forces in the engagement
of contact and contact members when a module is being installed
in the cabinet or withdrawn from the cabinet. The modules are
firmly supported and latched in place. The withdrawing or
inserting normally is a single-handed operation.
